Pressure treatment of various materials or devices, such as, for example, medical or dental instruments, in order to sterilize them has been used as an alternative to more common high temperature sterilization, such as steam sterilization, or high temperature washing. Steam sterilization generally requires an autoclave in which the instruments to be sterilized are placed, and a means for supplying steam to the autoclave. Such an arrangement is shown, for example, in U.S. Pat. No. 3,415,613 of Wallden. One of the disadvantages to such an arrangement is the danger inherent in using steam, which necessitates the use of expensive valving and steam conduit to minimize the possibility of leaks and accidental discharge of the steam.
Another type of sterilization process is liquid chemical sterilization, which requires a post treatment rinsing step, with the concomitant danger of recontamination, and gaseous disinfecting, such as with formaldehyde gas, which normally also requires an elevated temperature. In U.S. Pat. No. 4,973,449 of Kolstad et al. there is shown a method and apparatus for sterilizing dental instruments, for example, in which the instruments to be sterilized are placed in a sterilizing chamber and then subjected to relatively low and relatively high pressures in the presence of a sporicide atmosphere, which may comprise a mixture of formaldehyde, alcohol and water vapors, at a temperature in the range of 120.degree. F. to 160.degree. F. With the instruments in the chamber, the pressure in which is near a vacuum, a pressure pulse of vapor is introduced therein, the pressure being in the range of 25 psi to 40 psi above the starting pressure, and then the pressure is reduced to approximately the starting pressure. A preferred rate of pulsing is given as twenty discrete pulses within a two minute pulsing period. The actual sterilization depends on the sporicidal atmosphere, and the pulsing is alleged to enhance the effectiveness of that atmosphere. In addition, the process requires a relatively complex valving system to achieve the desired pulses.
Other sterilization arrangements use sterilization gas (U.S. Pat. No. 3,944,387 of Schreckendgust), and saturated steam (U.S. Pat. No. 4,944,919 of Powell).
The various prior art arrangements, which for the most part, depend upon heat (steam), radiation, or chemicals (formaldehyde vapor) are not practical where the material to be sterilized may consist, for example, of biomolecules, since desirable organisms may be destroyed along with undesirable organisms. Thus, it has been necessary to find alternative sterilization techniques, such as hydrostatic pressure sterilization, where the microorganisms are subjected to pressures as great as 3000 bar. Good experimental results in which unwanted microorganisms have been destroyed have been reported, but no definitive structure or system apparently has been proposed. See, for example, "Pressure Inactivation of Microorganisms at Moderate Temperatures" by P. Butz and H. Ludwig, Physica 139 and 140B (1986), North-Holland, Amsterdam at pp. 875-877.
Thus, while purely hydrostatic pressure treatment eliminates the dependence on high temperatures and/or chemical vapors for sterilization, with their attendant handling problems, the factors of versatility, convenience, economy, and simplicity have not been adequately addressed, nor have the pressures used nor the pressure redirection rates been sufficiently great to accomplish complete sterilization.